The invention relates to an electrical circuit arrangement for converting an electrical input variable (voltage or current) into an impressed electrical output voltage, there being a predefined relationship between the input variable and the output voltage.
In automation equipment, actual values and setpoint values, as well as control signals, are being increasingly linked by microprocessors. In many cases, the actual values and setpoint values are present as analog signals, for example in the form of electrical voltages or currents. As microprocessors can only process digital signals, the analog signals must be digitized before they can be processed by the microprocessor. The digitization is usually carried out in such a way that an analog/digital converter converts an electrical voltage between 0 V and +5 V into a digital signal which is suitable for processing by a microprocessor. A voltage of 0 V in this case corresponds to a signal value of 0%, and a voltage of +5 V corresponds to a signal value of 100%. In order also to process voltages with a different signal range, for example from 0 V to +10 V or from xe2x88x9210 V to +10 V, or currents with a signal range from for example 0 mA to 20 mA, the signals must have previously been converted into the signal range of 0 V to +5 V which is provided for the analog/digital conversion. For this purpose, depending on the application case, circuit arrangements are used which convert a voltage into a voltage, or circuit arrangements which convert a current into a voltage. It is thus necessary to stock respective different circuit arrangements for the different electrical input variables.
The invention is based on the object of providing a circuit arrangement of the type mentioned at the beginning which makes it possible to convert the electrical input variables with different signal ranges into an impressed output voltage for a common signal range.
The invention brings about a reduction in the variety of types and thus lowers the costs for stockkeeping. Futhermore, it is also possible later to use actual value transmitters which have a different signal range from the originally provided actual value transmitters. In this case, the same circuit arrangement can continue to be used to convert the input variable.
Advantageous developments relate to refinements for the advantageous circuit implementation of the circuit arrangement according to the invention.